Essentially a cramp is an involuntary and forcible contraction of a muscle that then does not relax. Severe cramping may be followed by a tenderness in the muscle that may last some time.

Many people suffer from cramping – usually in the legs or feet.
Sometimes cramping of the legs at night can be due to the position the people lie
especially if the knees are slightly bent and the feet pointing down. in this type of position the calf muscle will be relaxed (shortened) and can be prone to cramping. The same can happen if sitting for prolonged periods in the same position

Often, the addition of extra magnesium will help.

To correct this you can start taking Colloidal minerals, which have a good balance of both calcium and magnesium but also contain all other trace elements.
In some cases the addition of extra magnesium for the first few weeks is necessary.
See pages on ‘Minerals – facts’ andMinerals – why we need to supplement’..

There is also the possibility that there is some nerve damage, most likely in the lumbar spine. I have noted many times that people suffering from leg cramps will report that they gain relief after having an Osteopathic treatment.